Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.39	7.667%	$128.5436	$128.54	$128.55	$128.50
Purchase #2	$40.87	6.649%	$43.5874	$43.59	$43.60	$43.60
Purchase #3	$210.73	4.819%	$220.8851	$220.89	$220.90	$220.90
Purchase #4	$37.84	4.693%	$39.6158	$39.62	$39.60	$39.60
Purchase #5	$12.97	5.382%	$13.668	$13.67	$13.65	$13.70
Purchase #6	$244.80	3.466%	$253.2848	$253.28	$253.30	$253.30
Purchase #7	$162.38	10.441%	$179.3341	$179.33	$179.35	$179.30
7 purchase totals =	$828.98		$878.9188	$878.92	$878.95	$878.90